Malignant histiocytosis. A phenotypic and genotypic investigation.

Ten cases of malignant histiocytosis (MH) were evaluated for clinical and histopathologic features, phenotype, and rearrangement of T cell receptor (TCR) beta, gamma, and alpha and immunoglobulin (Ig) genes (7/10). All cases were HLA-DR+ and CD30-positive. Four cases had molecular evidence of T cell lineage such as TCR beta, gamma, and alpha rearrangements, and one additional case synthesized the cytoplasmic TCR beta chain. The remaining five cases did not show unequivocal T, B, natural killer (NK) cell, or macrophagic origin, and three of them had germline TCR and Ig genes. Ultrastructural analysis was not helpful for the definition of the cell lineage. Most myelomonocytic markers (MAC387, CD13, CD14, CD64, CD68) were either negative on the MH cells or were expressed on cells with rearranged TCR gene. Precursor (CD34, CD7) and NK (CD16, CD56, and CD57) cell markers were not found. The lineage of a number of cases of MH remains unresolved.     

Genotypic analysis in large cell lymphomas expressing a restricted set of differentiation antigens

Immunophenotyping and immunogenotyping were performed in a series of 8 large cell lymphomas exhibiting anaplastic or "histiocytic" morphology and displaying an uncertain phenotype due to a restricted number of differentiation antigens. 6 cases expressed the Ki-1 antigen. 4 cases expressed one or two B-cell markers and contained rearrangements of the immunoglobulin genes. One of them also exhibited a T-cell receptor (TCR) beta gene rearrangement. 3 cases expressed a single T-cell differentiation antigen. Among them, only 1 displayed both gamma and beta TCR gene rearrangement; 1 only contained a gamma TCR gene rearrangement and 1 completely lacked clonal rearrangements. The eight cases expressed an inconclusive immunophenotype due to an abundant population of reactive cells but showed an immunoglobulin gene rearrangement. In conclusion, 5 out of the 8 unusual lymphomas studied here could be characterized by immunogenotyping. This approach was, however, inconclusive in the 3 remaining cases, whose lineage and differentiation stage remain poorly defined.     

T cell lymphoma co-expressing CD20

Haematological malignancies are currently classified by the WHO according to lineage, with stratification of non-Hodgkin lymphomas into B cell neoplasms, and T and NK cell neoplasms. Many laboratories routinely use CD20 and CD3 immunostains to identify B and T cell lymphomas respectively, with the use of additional immunomarkers where necessary.We report a case of an 84-year-old male with a peripheral lymphoma which stained positively with both CD3 and CD20. PCR of DNA extracted from paraffin embedded material was positive for clonal T cell receptor gene rearrangements but negative for clonal immunoglobulin gene rearrangement supporting a diagnosis of T cell lymphoma with aberrant CD20 positivity.This case is one of only a small number of reported cases of T cell lymphoma co-expressing CD20 and illustrates a potential pitfall in diagnosis. It emphasizes the need for 1) vigilant review of immunohistochemical stains to avoid misinterpretation and 2) the use of a wide immunohistochemical panel in lymphoma diagnosis with additional molecular studies where necessary.     

血液系统肿瘤患者外周血细胞IgH基因和TCRγ基因的检测及意义

检测各种血液系统肿瘤患者外周血细胞免疫球蛋白重链基因 (IgH )和T细胞受体γ基因 (TCRγ )克隆性重排并探讨其意义。通过多聚酶链式反应 (PCR )方法检测 32例非霍奇金淋巴瘤 (NHL )、 18例急性髓性白血病 (AML )、 2 4例多发性骨髓瘤 (MM )、 8例急性淋巴细胞白血病 (ALL )及 6例慢性淋巴细胞白血病 (CLL )患者外周血细胞IgH及TCRγ克隆性基因重排。结果表明 ,NHL、AML、MM、ALL及CLL患者中IgH克隆性重排率分别为 37 5 0 %、 2 2 2 2 %、 83 33%、 12 5 0 %和 16 6 7% ;TCRγ基因克隆性重排率分别为 6 2 5 0 %、 5 0 0 0 %、 5 4 17%、 5 0 0 0 %及 5 0 0 0 %。在B型、T型NHL中 ,IgH克隆性重排率分别为 31 5 8%及 6 6 6 7% ;TCRγ克隆性重排率分别为 47 37%及 6 6 6 7%。AML中IgH克隆性重排阳性者的初治完全缓解率(CR ) (5 0 0 0 % )与IgH重排阴性的初治CR率 (5 0 0 0 % )无显著差异 (P >0 0 5 )。TCRγ克隆性重排阳性者与阴性者的初治CR率 (均为 44 44 % )亦无显著差异 (P >0 0 5 )。IgH及TCRγ基因克隆性重排不具有细胞谱系的特异性 ,但通过检测外周血IgH、TCRγ克隆性基因重排对NHL有辅助诊断意义 ,并且可作为监测微小残留病壮 (MRD )的手段。     

Lymphocytic infiltrates of the conjunctiva and orbit: immunohistochemical staining of 16 cases

The authors have performed frozen section immunologic stains on 16 cases of ocular lymphocytic infiltrates and correlated the results with clinical and histologic findings. Their cases included inflammatory pseudotumor (3), reactive lymphoid hyperplasia (3), atypical lymphocytic infiltrate (9), and small cleaved cell lymphoma (1). Seven of the nine cases with an atypical lymphocytic infiltrate expressed one immunoglobulin light chain, while only one of six considered reactive on histologic evaluation had immunologic results suggestive of a neoplastic B cell proliferation. The case of follicular small cleaved cell lymphoma expressed B lineage antigens but did not express immunoglobulin; this patient died of disseminated lymphoma two years after conjunctival involvement. Percentages and subset ratios of T lymphocytes were quantitated and showed similar results in reactive and neoplastic lesions. There is no apparent difference in clinical presentation or follow-up information between patients with reactive lesions and those having an atypical lymphocytic infiltrate with monotypic immunoglobulin.     

T-cell receptor beta chain gene rearrangements: genetic markers of T-cell lineage and clonality

We have performed a series of investigations involving T-cell receptor beta chain (T beta) gene rearrangements in benign and malignant nonhematopoietic, B-cell, and T-cell proliferations. These studies provide the conceptual basis and the operational approach for the use of T beta gene rearrangements as markers of T-cell lineage, clonality, and differentiation, analogous to immunoglobulin gene rearrangements in B cells. Southern blot hybridization analysis for T beta gene rearrangements can now be utilized to identify and distinguish between non-T cells, polyclonal T cells, and monoclonal T cells. Determination of T beta gene rearrangements will play an important role in the further investigation and classification of T-cell neoplasia. However, the identification of a genetic marker of clonality for T cells has significant diagnostic and prognostic value as well. For example, determination of the T beta gene rearrangement unique to a particular malignant T-cell clone provides a specific genetic marker for that clonal T-cell proliferation. This genetic marker of the T-cell clone may provide a useful tool for monitoring the patient's therapeutic response and clinical course for early signs of relapse. Nonetheless, our studies demonstrate that the lineage specificity of immunoglobulin and T beta gene rearrangements is not absolute. It appears that only a multiparametric approach combining extensive monoclonal antibody immunophenotypic analysis, in vitro testing for functional help and suppression, and Southern blot hybridization analysis for immunoglobulin and T beta gene rearrangements allows the conclusive and unequivocal demonstration of the B- or T-cell derivation of all lymphoid neoplasms. Lymphoid malignancies that cannot be assigned to the B- or T-cell lineage following this extensive multiparametric analysis are exceedingly uncommon.     

Clonal rearrangements of immunoglobulin genes and progression to B cell lymphoma in cutaneous lymphoid hyperplasia.

Cutaneous lymphoid hyperplasia (CLH) is a disorder characterized by the development of one or more skin lesions containing dense lymphoid infiltrates that exhibit the histopathologic features of a benign, reactive process. Nevertheless, some cases have been associated with the subsequent development of clinically overt lymphomas. This suggests that monoclonal populations may exist in some cases of CLH and that these cases may represent a subset more likely to evolve into lymphoma. To determine if such a subset of CLH can be distinguished, Southern blot analysis of DNA was used to study the immunogenotypic features of lesions from 14 patients with clinical, histopathologic, and immunopathologic findings characteristic of CLH. Five cases exhibited detectable clonal rearrangements of immunoglobulin genes. Furthermore, one of these five cases evolved into overt diffuse large cell lymphoma of B cell lineage during a 2-year follow-up of recurrent disease at the original cutaneous site. The immunoglobulin gene rearrangements of this lymphoma were identical to those of the prior CLH lesion. There was no evidence of detectable t(14;18) chromosomal translocations or clonal rearrangements of the beta gene of the T cell receptor in any case. It was concluded that CLH can be divided into two subsets based on the presence or absence of a clonal B cell population, and that overt lymphoma can arise from the former subset and contain the same B cell clone identified in the pre-existent CLH lesion.     

Frequent T and B cell oligoclones in histologically and immunophenotypically characterized angioimmunoblastic lymphadenopathy

The identification of clonal rearrangements of T cell receptor (TCR) genes is central to the diagnosis of T cell lymphomas. However, in angioimmunoblastic lymphadenopathy (AILD), first described as a nonneoplastic proliferation associated with immunodeficiency, the heterogeneity of TCR and IgH gene rearrangements suggest that some cases may harbor multiple lymphoid clones. In this study we have isolated DNA from archival paraffin biopsy material from 22 cases of AILD identified on the basis of classical histological and immunohistochemical features with the aim of establishing the occurrence of clones and oligoclones, the frequency of TCR and immunoglobulin heavy chain (IgH) variable (v) gene use, and the relationship of these findings to the presence of Epstein-Barr virus. DNA extracted from the biopsies was amplified using the polymerase chain reaction (PCR) and sequenced to detect functional and nonfunctional gene rearrangements. Epstein-Barr virus-encoded short RNA species (EBERs) were detected using in situ hybridization combined with immunochemistry to identify the phenotype of the Epstein-Barr virus-infected cells. Fifty-seven clonal products were found in 20/22 patients: TCRgamma clonal products were identified in 16/22, TCRbeta clonal products in 16/22 and IgH clonal products in 6/22 cases. Oligoclonal PCR products were seen for TCR in 3/22 and for IgH in 3/22 cases. In one biopsy PCR products from all reactions were polyclonal. Sequence analysis revealed functional TCRgamma, TCRbeta, and IgH sequences in 6/12, 9/11, and 8/8 cases, respectively. Functional TCR and/or IgH oligoclones were detected in 6/20 (30%) cases. In addition, nonfunctional TCR and IgH sequences were found in 11 cases. EBERs were identified in 18/20 cases varying from occasional to 25 to 30% nuclei staining and were associated with both T and B cells, although the majority were of indeterminate phenotype. The presence of EBERs was not associated with all clonal IgH gene rearrangements but was associated with B cell oligoclones. Patterns of gene recombinations indicated that the majority of TCRgamma recombinations used GV1 and GJ1S3/2S3 genes. Six out of eleven cases used TCR BV4S1 or BV2S1 genes associated with various BJ and BD1/2 genes. No common IgH gene usage was identified, but 8 clones had varying degrees of replacement and silent mutations (0.6-10.1%), consistent with B cell clones having undergone somatic mutation in the germinal center, and 3 clones harbored unmutated V genes, consistent with naive B cells. Our data do not support the concept of AILD as a clearly defined peripheral T cell lymphoma (PTCL). Rather, they suggest that AILD as defined by histology and immunohistochemistry is either a heterogeneous entity or represents a lymphoproliferation associated with immunodeficiency in which clonal T cell or B cell proliferation may occur.     

Most null large cell lymphomas are B lineage neoplasms

DNA of immunoglobulin and the beta T cell receptor genes was analyzed for rearrangements in 34 diffuse large cell lymphomas that failed to express immunoglobulins or T cell antigens. Twenty-eight cases had both heavy and light chain immunoglobulin rearrangements, two cases had only heavy chain gene rearrangements, three cases had only light chain gene rearrangements, and one case failed to show rearrangements for any of the immunoglobulin genes. None of the cases showed rearrangements for the beta T cell receptor gene. These results indicate that the vast majority of diffuse large cell lymphomas that lack definitive B or T cell phenotypic markers are actually B cell in origin.     

Immunophenotypic and genotypic characterization of diffuse mixed non-Hodgkin's lymphomas

Diffuse, mixed small and large cell lymphomas (DML) are a heterogeneous group of non-Hodgkin's lymphomas. There are only a few published immunophenotypic and/or genotypic studies of DML, and they include a small number of cases. It is unclear whether these neoplasms are monoclonal, oligoclonal, or perhaps of dual lineage. Using monoclonal antibodies (UCHL1, MB2, MT1, LN1, LN2, and L26) that are effective in paraffin-embedded, B5-fixed tissue, 13 cases of DML were studied. This method allowed for improved correlation between cell morphology and immunophenotype compared with frozen section immunohistology. In addition, Southern blotting/DNA hybridization was used to identify directly the lineage of the neoplastic cell population. In each case a population of large B lymphocytes was demonstrated by immunohistology. In six of the cases, a single class of immunoglobulin light chains was detected by frozen section immunohistology, cytospin immunocytology, or both supporting the hypothesis that the B lymphocytes are monoclonal. In almost all the cases (12 of 13), the small cell population consisted predominantly of T lymphocytes. Immunoglobulin gene rearrangements were detected in seven cases, but no T cell receptor gene rearrangements were detected. It was concluded that DML are monoclonal lymphomas of B cell lineage with a non-neoplastic T cell component.     

Genotypic and immunophenotypic analysis of anaplastic large cell lymphoma (Ki-1 lymphoma)

Genotypic and immunological analysis was performed in 10 patients with anaplastic large cell lymphoma (Ki-1 lymphoma), 4 were male and 6 female. Immunophenotypically, 9 of these patients expressed some T cell markers; CD 2 in 9, CD 4 in 9, CD 3 in 6, CD 8 in 4, and UCHL-1 in 8. For B cell markers, 4 patients expressed B 1 and one expressed L 26; these patients also expressed T cell markers. In genotypic analysis, 9 of 10 cases displayed some incidence of T cell receptor gene (TCR) rearrangement or deletion, which was found in 3 patients for C beta 1, 7 for C beta 2, 8 for J gamma, 5 for C gamma (Hind III), 5 for C gamma (EcoRI), 3 for J delta 1 (Hind III), 3 for J delta 1 (BamHI), 3 for J delta 2, and 2 for C delta. One patient with rearrangement of TCR also showed rearrangement of immunoglobulin heavy chain. Another patient exhibited rearrangement of both TCR and immunoglobulin chain. These results indicate a common T cell lineage for this type of lymphoma.     

Clonality of CD3 negative large granular lymphocyte proliferations determined by PCR based X-inactivation studies.

AIMS--To examine persistent CD3-large granular lymphocytosis (LGL) cases for clonality, both by lineage specific (T cell receptor) and lineage independent (X-inactivation) molecular methods; and to find out whether X-inactivation studies are more appropriate than gene rearrangement studies for this subset of LGL disorders. METHODS--Patients were selected who had LGL of more than six months' duration and identified as CD3- by immunophenotyping. T cell receptor studies and, where possible, X-inactivation studies of the phosphoglycerate kinase (PGK) gene were carried out. Analysis of subpopulations was carried out on cases heterozygous for PGK by the use of a polymerase chain reaction (PCR) method for X-inactivation. RESULTS--Of 17 CD3- LGL cases studied, all were found to be germline for beta, gamma, and delta T cell receptor studies, and immunoglobulin heavy chain genes. However, six of these were analysed by X-inactivation of the PGK gene and two cases gave clonal band patterns but only within the CD3- subpopulation. CONCLUSIONS--Clonal analysis by the lineage independent method of X-inactivation allows clonal expansion undetected by T and B cell specific markers to be identified. It is therefore a more appropriate method for the analysis of CD3- LGL. This has implications for diagnosis in CD3- LGL disorders.     

Immunohistochemical, molecular, and cytogenetic analysis of a consecutive series of 20 peripheral T-cell lymphomas and lymphomas of uncertain lineage, including 12 Ki-1 positive lymphomas

Although several independent series of non-Hodgkin's lymphomas (NHLs) have been subjected to cytogenetic studies or analyses of lineages by assaying for clonal immunophenotypes and clonal rearrangements affecting immunoglobulin (IG) and T-cell receptor (TCR) genes, no published reports exist of series of non-B-cell NHLs on which cytogenetic, immunohistochemical, and IG and TCR gene rearrangement studies have been undertaken together. Among 343 NHLs ascertained prospectively between January 1984 and December 1988 at the Memorial Sloan-Kettering Cancer Center, 278 cases with clonal chromosome abnormalities were identified. Of the latter, 20 were non-B-cell NHLs, which in turn comprised 15 peripheral T-cell lymphomas (PTCLs) and 5 lymphomas of uncertain lineage (LULs). The LULs either were biogenotypic, had discordant immunophenotype and immunogenotype, or showed no evidence of B-cell, T-cell, or histiocytic derivation. Of the 15 PTCLs, eight expressed the Ki-1 antigen and four of these had translocations involving the band 5q35 [t(5q35)]. Of the five LULs, four expressed the Ki-1 antigen and one of these had a translocation involving band 5q35. Previous studies have associated t(5q35) with Ki-1 positive NHLs characterized histologically by a pleomorphic diffuse large cell morphology. In our series of 12 Ki-positive non-B-cell NHLs, five (42%) had a 5q35 translocation. They were histologically indistinguishable from the subset without the translocation. The frequent lineage uncertainty exhibited by Ki-1 positive NHLs of similar histology and cytogenetic abnormalities suggests their derivation from an early uncommitted lymphoid cells.     

Chronic myelomonocytic leukaemia associated with T cell receptor delta gene rearrangement.

Morphological, immunophenotypic, and genetic analyses were carried out on peripheral blood, bone marrow, and pharyngeal biopsy material from a patient with chronic myelomonocytic leukaemia (CMML). Morphological analysis of bone marrow was diagnostic of CMML; immunophenotypic analysis of peripheral blood and bone marrow were negative for B and T cell antigens, and immunochemistry performed on the pharyngeal extramedullary infiltrate showed the presence of large monocytoid cells which stained positively for muramidase. Genotypic analysis, however, showed clonal rearrangement of the T cell receptor (TCR) delta chain gene, a marker of T cell or, less commonly, B cell lymphoid neoplasms. Other TCR genes, beta and gamma, were germline in all tissues examined. TCR delta is rearranged in precursor B cell and most T lymphoid neoplasms. A small proportion of cases (10%) of acute myeloid leukaemia (AML) also show rearrangement of the TCR delta gene. To date TCR delta rearrangement has not been described in CMML. The aberrant TCR delta rearrangement shown in this patient with CMML provides further evidence of the clonal nature of this disorder.     

Rearrangement of kappa-chain and T-cell receptor beta-chain genes in malignant lymphomas of "T-cell" phenotype

Detection of immunoglobulin gene rearrangements by molecular hybridization is considered to be a highly sensitive approach to the evaluation of clonality of B-cell-derived neoplasms. Like monoclonal surface immunoglobulin in B cells, which serves as a reliable immunophenotypic marker for clonality, rearrangement of the genes encoding immunoglobulin light chains has been accepted as a reliable genotypic marker for the presence of a clonal expansion of B lymphocytes. The authors now report 3 cases of non-Hodgkin's lymphoma that were immunologically classified as having a T-cell phenotype and in which, in addition to rearrangements of the T-cell receptor beta-chain gene, a rearrangement of an immunoglobulin light-chain gene was clearly identified by Southern blot hybridization. The results demonstrate that the data obtained by molecular hybridization should be interpreted with caution when the immunogenetic findings do not correlate with immunophenotypic expression, and that the results of molecular genetics studies should be interpreted in conjunction with morphologic and immunologic findings.     

Sensitivity of PCR in detecting monoclonal B cell proliferations.

AIMS--To evaluate the rapid detection of various forms of monoclonal B cell proliferations by using the polymerase chain reaction (PCR) to identify clonal immunoglobulin heavy chain genomic rearrangements. METHODS--Thirty four B cell lymphomas defined by morphology, immunophenotyping, and positive immunoglobulin heavy chain gene rearrangements detected by Southern blot analysis were examined. An additional 22 cases representing miscellaneous lymphoproliferative and non-lymphoproliferative disorders were also studied. RESULTS--Monoclonal rearrangements were identified in 19 (56%) cases of B cell lymphoma. The method was less sensitive in the detection of follicular centre cell lymphomas (15 of 28, or 54%) than non-follicular centre cell lesions (four of six, or 67%). Monoclonal rearrangement was not identified in 19 control cases, including T cell lymphomas, Hodgkin's disease, reactive lymphadenopathy and metastatic carcinoma. Three cases showed positive immunoglobulin gene rearrangement by PCR but were negative on Southern blotting. Two of these cases had definite clinical, morphological, and immunophenotypic evidence of monoclonal B cell proliferation suggesting that PCR could, on occasion, pick up cases missed by Southern blotting and that the two methods are complementary in clonal lymphoproliferative disease diagnosis. The third case represented a "false positive" PCR reaction involving a colonic adenocarcinoma. CONCLUSIONS--PCR analysis, using the primer sequences outlined in this study, will detect about 55% of clonal lymphoproliferative proliferations with increased sensitivity for non-follicular centre cell lesions. With these levels of detection in mind, this testing strategy can still be especially useful in cases which prove diagnostically problematic with standard morphological and immunophenotypic analysis, and in instances where the quantity and type of diagnostic material is limiting (needle aspirates and cellular fluids).     

Multiple T-cell clones specific for the same foreign pMHC ligand can be generated from a single, ancestral TCR-VDJbeta precursor

Owing to ordered, stage-specific T-cell receptor (TCR) gene rearrangements and cell division during T-cell development, small cohorts of "half-sibling" T cells sharing an ancestral TCR VDJbeta rearrangement but expressing different TCR alpha-locus rearrangements may be selected into the mature T-cell repertoire. We wondered whether different alphabetaTCRs expressed by T cells from the same ancestral VDJbeta cohort might be capable of recognizing the same foreign peptide-major histocompatibility complex complex (pMHC). By a combined flow cytometric and single-cell polymerase chain reaction (PCR) approach to analyze TCRs selected by the previously defined foreign antigen, pCW3170-179/H-2Kd, we were able to identify cohorts of half-sibling antigen-specific CD8 T cells after their expansion in immunized mice. We amplified residual DJbeta rearrangements as clonal markers to confirm that the shared VDJbeta sequences represent ancestral rearrangements rather than identical but independent ones. An intriguing explanation of our findings would be that only a very limited repertoire of TCR alpha-chains is selected to pair with a given TCR beta-chain during T-cell development.     

Acute lymphoblastic leukaemia: correlation between morphological/immunohistochemical and molecular biological findings in bone marrow biopsy specimens.

BACKGROUND: Although numerous antibodies suitable for use on paraffin wax embedded sections are available for the subtyping of acute leukaemia (acute myelogenous leukaemia (AML) and acute lymphoblastic leukaemia (ALL)) in bone marrow biopsy sections, unequivocal identification of the cell line involved is sometimes impossible. METHODS: Forty eight formalin fixed, paraffin wax embedded bone marrow biopsy specimens that had been decalcified in EDTA were investigated, including 42 thought to exhibit ALL on the basis of bone marrow smears. Five specimens exhibited AML and one biphenotypic leukaemia, as diagnosed immunohistochemically in bone marrow biopsies. Immunostaining was performed with antibodies against relatively specific B and T cell antigens. The blasts were investigated for rearrangements of the immunoglobulin heavy chain (IgH) and the T cell antigen receptor (TCR) genes. RESULTS: Amplifiable DNA was obtained from all 48 specimens. An IgH gene rearrangement was detected in 20 of 23 c-ALL specimens. Four of seven T cell ALL (T-ALL) specimens had a TCR-gamma gene rearrangement, and the one B cell ALL (B-ALL) specimen exhibited a clonal IgH gene. Three of four cases of unclassifiable ALL could be assigned to the B cell lineage on the basis of gene rearrangement analysis. Seven cases originally diagnosed in smears as ALL were rediagnosed as AML (n = 5) or biphenotypic leukaemia (n = 2) because of immunohistochemical reactivity for myeloperoxidase or lysozyme. Two of these AML cases and two of three cases of biphenotypic leukaemia exhibited a monoclonal IgH gene rearrangement. CONCLUSIONS: Acute leukaemia can be subtyped in bone marrow sections with a limited panel of antibodies suitable for use on paraffin wax embedded sections (against CD3, CD10, CD20, CD79a, myeloperoxidase, and lysozyme). In patients with ALL and a diagnostically equivocal immunophenotype, gene rearrangement analysis might indicate whether the B or T cell lineage is involved.     

Rearrangement of immunoglobulin and T-cell receptor genes in Hodgkin''s disease.

The precise cellular origin of the malignant cell population in Hodgkin's disease (HD) is unknown. Recent application of Southern blotting techniques to detect clonal rearrangements of immunoglobulin (Ig) and T-cell receptor (TCR) genes has yielded conflicting results. The authors report the detailed analysis of tumor tissue DNA obtained from 18 cases of HD using Ig and TCR gene probes. The distribution of HD subtypes was similar to that in other series. Samples were examined for rearrangement by means of multiple restriction enzymes with specific probes for the Ig heavy chain, Ig kappa, Ig lambda, TCR beta, and TCR gamma loci. Only germline bands were detected in all 18 cases with the Ig gene probes and in 15 of 18 cases with the TCR probes. In 2 cases blot analysis suggested a predominance of polyclonal (or oligoclonal) T cells. In 1 case monoclonal rearrangement of the TCR beta gene was detected. Based on the intensity of the rearrangement and the small percentage of Reed-Sternberg (R-S) cells in this case, the clonal population detected was most likely not the R-S cell itself. The data do not support the frequent occurrence of Ig or TCR monoclonal gene rearrangement in HD.     

Composite low grade B-cell lymphomas with two immunophenotypically distinct cell populations are true biclonal lymphomas. A molecular analysis using laser capture microdissection.

Low grade B-cell lymphomas comprise several well defined, clinically and immunophenotypically distinct disease entities. Composite lymphomas showing phenotypic characteristics of more than one of these tumor subtypes in the same site are rare, and both common and separate clonal origins of the two tumor parts have been reported for cases studied by molecular methods. We describe the detailed immunohistochemical and molecular findings in three cases with features of composite low grade B-cell non-Hodgkin's lymphoma (B-NHL). All three neoplasms contained morphologically distinct but interwoven compartments of different cell types, which exhibited discordant expression of several markers, including CD5, CD10, CD43, and cyclin D1. According to their morphology and phenotypes, they were classified as mantle cell lymphoma and follicular lymphoma (Case 1), follicular lymphoma and small lymphocytic lymphoma (Case 2), and mantle cell lymphoma and chronic lymphocytic leukemia/small lymphocytic lymphoma (Case 3). PCR analysis of DNA obtained from whole tissue sections failed to reveal evidence for biclonality in any of the cases. We therefore isolated cell populations with different antigen expression patterns by laser capture microdissection and analyzed them by polymerase chain reaction amplification and sequencing of clonal immunoglobulin heavy chain gene rearrangements and oncogene rearrangements. Sequence analysis revealed unrelated clonal rearrangements in each of the two tumor parts in all three cases, suggesting distinct clonal origins. In addition, Case 1 showed a bcl-2 rearrangement present only in the follicular lymphoma part. Our findings suggest that low grade B-NHL with two distinct morphological and immunophenotypic patterns in the same anatomical site are frequently biclonal. This is in keeping with current classification schemes, which recognize subtypes of low grade B-NHL as separate disease entities. Furthermore, our analysis demonstrates the power of laser capture microdissection in revealing molecular microheterogeneity in complex neoplasms.